Get event targetting working for mouse events.

ui/events/event_dispatcher_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/event_dispatcher.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/events/event.h"
 #include "ui/events/event_dispatcher.h"
 #include "ui/events/event_target.h"
@@ skipping 28 matching lines @@
  private:
   // Overridden from EventTarget:
   virtual bool CanAcceptEvent(const ui::Event& event) override {
     return true;
   }
 
   virtual EventTarget* GetParentTarget() override {
     return parent_;
   }
 
-  virtual scoped_ptr<EventTargetIterator> GetChildIterator() const override {
+  virtual scoped_ptr<EventTargetIterator> GetChildIterator() override {
     return scoped_ptr<EventTargetIterator>();
   }
 
   virtual EventTargeter* GetEventTargeter() override {
     return NULL;
   }
 
   TestTarget* parent_;
   std::vector<int> handler_list_;
   bool valid_;
@@ skipping 540 matching lines @@
     NonCancelableEvent event;
     EventDispatchDetails details = dispatcher->ProcessEvent(&target, &event);
     EXPECT_TRUE(details.dispatcher_destroyed);
     EXPECT_EQ(2U, target.handler_list().size());
     EXPECT_EQ(1, target.handler_list()[0]);
     EXPECT_EQ(2, target.handler_list()[1]);
   }
 }
 
 }  // namespace ui